html,
body {
    background-image: url(../images/building_dark.png);
    background-repeat: no-repeat;
    background-position: center;
    background-size: cover;
}

.hall_container {
    height: calc(100% - 50px);
    display: flex;
    justify-content: center;
    align-items: center;
}

#screen {
    width: 450px;
    height: 50px;
    margin-top: 10px;
    background-color: #fff;
    font-size: 22px;
    line-height: 50px;
    text-align: center;
}